1. Field of the Invention
This invention relates to a novel multi-layer structure polymer having excellent weatherability, etc., and a thermoplastic resin composition containing the multi-layer structure polymer and being excellent in weatherability, impact resistance and appearance.
2. Related Art
Polycarbonate and methacrylic resins have comparatively better weatherability among plastics. Since, however, their mechanical strength, processability, price, etc., are not necessarily well-balanced from the general point of view, their application fields are limited.
On the other hand, ABS resin has excellent impact resistance and well-balanced mechanical properties, and is also easily processable and comparatively less expensive. Due to these advantages, it is widely used in fields of automobile, electric parts, etc. However, since the ABS resin uses polybutadiene as one of its components, it involves a problem concerning weatherability, and is thought to be unsuitable in fields for outdoor use. Thus, it has been long desired to develop plastics containing an ABS resin in which the weatherability is remarkably improved.
Under the above circumstances, it has been taken into consideration to use rubbers other than diene-based rubbers, and the use of saturated rubbers has been proposed at various times. An acrylic acid ester-based polymer is one of the rubbers proposed. Its use makes it possible to improve the weatherability, but does involve a degradation of the impact resistance and appearance of molded articles made therefrom, which results in a problem in its practical use.
For example, Japanese Patent Publication No. 27576/1980 discloses a process for producing a multi-stage, consecutive structure polymer comprising a hard polymer produced at a first stage, a rubbery elastomer polymer produced at an intermediate stage and a hard polymer produced at a third stage. In this process, the use of a grafting agent and a crosslinking agent at the first stage gives a resin composition having low haze and impact resistance.
However, the scope of any practical use of the above resin composition is limited since it has low impact strength.
Japanese Patent Publication No. 36645/1984 discloses a process for producing a multi-stage polymer comprising methacrylic acid ester and acrylic acid ester. However, this polymer has insufficient impact resistance.